A communication system may include an optical-communication link where an optical transmitter and an optical receiver send or receive data using free-space optical communication. An optical-communication link may be a one-way link where one communication station transmits information to another communication station, or a communication link may be bidirectional where both communication stations transmit and receive information. An optical-communication link may have a data rate between 1 megabit per second and 100 gigabits per second. For example, a free-space optical-communication link may have a data rate of 10 gigabits per second. In a free-space optical-communication link, an optical transmitter and an optical receiver may be separated by relatively short distances (e.g., 1 m to 1 km) or moderate to long distances (e.g., 1 km to 36,000 km).
An optical transmitter and receiver may communicate using any suitable optical wavelength, such as for example, 405 nm, 780 nm, 1.3 μm, or 1.5 μm. An optical transmitter may transmit an optical signal by applying a current modulation to a laser diode or a light-emitting diode. An optical receiver may include a photodetector that converts received light from the transmitter into an electrical current. An optical receiver may also include a transimpedance amplifier that produces an output voltage signal based on the electrical current from the photodetector.